At the time, Trump said that he was happy to sign the nonbinding
pledge because the RNC assured him that it would treat him
"fairly."

But Trump's tweet on Monday suggested that he could be trying to
use a third-party run as leverage against the RNC again.

He also hinted at the possibility the day before during an
interview on ABC's "This Week." Host George Stephanopoulos
asked Trump about
a recent Wall Street Journal report on a supposed "guerrilla
campaign" being planned against him.

He asked if that could lead to Trump
rethinking his third-party pledge.

"Well, we'll see what happens," Trump replied,
according to ABC's transcript. "It will be very interesting.
But I'm leading every poll by a lot. It's not even a little bit
anymore, it's a lot."

Stephanopoulos pressed Trump again.

"Well, I'm going to have to see what happens," the candidate
repeated. "I will see what happens. I have to be treated fairly.
You know, when I did this, I said I have to be treated fairly. If
I'm treated fairly, I'm fine."

It's not clear whether the "guerrilla campaign" will ultimately
amount to a significant spending effort against Trump. That
campaign is reportedly being spearheaded by Liz Mair, a former
RNC online-communications director.

On Saturday morning, Trump and Mair also exchanged shots on
Twitter:

.@realDonaldTrump Thanks for raising my profile & name ID, Donald.I miss you (really!) on The Apprentice! Hope to get you back there soon :)